目录

摘要： ....................................................................................................................................... 2 1实验原理 ................................................................................................................................ 4 1.1调制 ................................................................................................................................ 4 1.2调幅电路分析 ................................................................................................................ 4 2 MATLAB仿真 .......................................................................................................................... 5 2.1 载波信号 ....................................................................................................................... 5 2.1.1 仿真程序 ............................................................................................................... 5 2.1.2仿真波形 ................................................................................................................ 6 2.2调制信号 ........................................................................................................................ 6 2.2.1 仿真程序 ............................................................................................................... 6 2.2.2仿真波形 ................................................................................................................ 7 2.3 AM调制 .......................................................................................................................... 8 2.3.1 仿真程序 ............................................................................................................... 8 2.3.2仿真波形 ................................................................................................................ 9 2.4 AM波解调（包络检波法） .......................................................................................... 9 2.4.1 仿真程序 ............................................................................................................... 9 2.4.2仿真波形 .............................................................................................................. 10 2.5 AM波解调（同步乘积型检波法） ............................................................................ 11 2.5.1 仿真程序 ............................................................................................................. 11 2.5.2仿真波形 .............................................................................................................. 12 2.6 AM波的功率 ................................................................................................................ 14 2.6.1 仿真程序 ............................................................................................................. 14 2.6.2仿真波形 .............................................................................................................. 15 2.7 调制度m对AM调制的影响 ....................................................................................... 15 2.7.1 仿真程序 ............................................................................................................. 15 2.7.2仿真波形 .............................................................................................................. 17 3结果分析： .......................................................................................................................... 18 4总结： .................................................................................................................................. 19

1

基于Matlab的AM振幅调制及解调仿真

摘要：本课程设计主要是为了进一步理解AM调制系统的构成及其工作原理，并能通过matlab软件来实现对AM调制系统的仿真，且通过对各个元件的参数进行不同的设置，来观察系统中各个模块的输出波形。在课程设计中，我们将用到matlab仿真平台，学习AM调制原理，AM调制就是由调制信号去控制高频载波的幅度，使之随调制信号作线性变化的过程。在波形上，幅度已调信号的幅度随基带信号的规律而呈正比地变化。解调方法利用相干解调。解调就是实现频谱搬移，通过相乘器与载波相乘来实现。通过相干解调，通过低通滤波器得到解调信号。相干解调时，接收端必须提供一个与接受的已调载波严格同步的本地载波，它与接受的已调信号相乘后，经低通滤波器取出低频分量，得到原始的基带调制信号。利用Matlab仿真建立AM调制的系统模型，用Matlab仿真程序画出调制信号、载波、已调信号、相干解调之后信号的波形以及功率频谱密度，分析所设计系统性能。

关键字：AM调制，解调，Matlab仿真，滤波

2

Abstract: This course is designed primarily to further understanding of the

composition and working principle of AM modulation system , and through matlab software to achieve the AM modulation system simulation , and the parameters of the various components through different settings , to observe the system output waveforms of respective modules. Curriculum design, we will use matlab simulation platform , learning AM modulation principle , AM modulation is controlled by the modulation signal to the amplitude of the high frequency carrier , making the process with the modulated signal as a linear change. On the waveform , the amplitude of the amplitude modulated signal is a baseband signal with the law and is proportional to the change . Demodulation method using coherent demodulation. Demodulation is to move the spectrum , multiplied by multiplication with the carrier to achieve. By coherent demodulation , a demodulated signal obtained through the low -pass filter. The coherent demodulation , the receiver must be provided with a local carrier wave modulated carrier received strict synchronization , after it is multiplied with the received modulated signal , the low pass filter to remove low frequency components to get the original modulating baseband signal . Create a system model simulation using Matlab AM modulation , using Matlab simulation program to draw modulated signal carrier modulated signal waveform signal after coherent demodulation and the power spectral density analysis of the design of the system performance.

Keywords: AM modulation, demodulation, Matlab simulation, filter

3